In DQMH 6.0 and later, and LabVIEW 2015 and later, you can right-click a Broadcast Event subVI and select Find DQMH Broadcast Event Frames:

After selecting this option, the tool will search all VIs in the active project for event structures registered for this broadcast event:

Once items appear in the list, you can double-click them to open the VI and highlight the event structure frame registered for the broadcast event: